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Faceted Gemstones: (these can also be cut as cabochons)
Click on the names to see pictures of gems and/or specimens and further information.
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Gemstone
Names
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Mineral
Species
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Chemical
Name
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Specific
Gravity
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Refractive
Index
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Hard-
ness
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Treatments
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Amethyst,
Citrine
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Quartz
purple, pink, brown, yellow and clear
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Silicon Oxide
SiO2
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2.64-2.69
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1.54-1.55
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6.5-7
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Sometimes heat treated.
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Emerald Aquamarine Morganite
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Beryl
‘chrome green’ blue to bl/green pink, yellow, clear, red
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Beryllium Aluminum Oxide
Be3Al2Si6O18
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2.67-2.90
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1.57-1.58
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7.5-8
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Emerald is often filled or oiled. The oil can be colored. Aquamarine is often heat treated.
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Diamond
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Diamond
white, yellow, pink, brown, blue, red
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Carbon
C
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3.51-3.53
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2.417
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10
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Sometimes filled. Colored diamonds are sometimes dyed.
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Tourmaline, Elbaite, Indicolite, Rubellite
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Tourmaline
almost any color you can imagine
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Complex Borosilicates
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3.00-3.26
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1.62-1.64
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7
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Sometimes filled & sometimes heat treated.
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Alexandrite
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Chrysoberyl
color change from red to green
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Beryllium Aluminum Oxide
BeAl2O4
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NA
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NA
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8.5
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Sometimes filled.
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Pyrope, Rhodolite, Tsavorite, Spessartine
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Garnet
red, rose to lavender, green, orange
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Various Silicates
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3.60-3.95
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1.74-1.76
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7-7.5
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Not usually treated.
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Peridot
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Olivine
apple green to yellow/green
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Magnesium Iron Silicate
(Mg,Fe)2SiO4
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3.27-3.48
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1.65-1.69
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6.5-7
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Not usually treated.
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Ruby, Sapphire
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Corundum
red, clear, blue, pink, yellow
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Aluminum Oxide
Al2O3
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3.95-4.10
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1.76-1.77
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9
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Often heat treated to enhance color.
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Topaz
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Topaz
clear, blue, pink, yellow, sherry
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Hydrous Aluminum Silicate
Al2SiO4(F,OH)2
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2.64-2.69
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1.62-1.63
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8
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Usually heat treated and/or irradiated.
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Tanzanite
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Zeosite
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Hydrous Calcium Aluminum Silicate
Ca2Al3(Si3O12)(OH)
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3.10-3.45
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1.62-1.70
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6-7
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Heat treated.
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Spinel
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Spinel
pink, blue, violet
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Magnesium Aluminum Oxide
MgAl2O4
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NA
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NA
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8
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Unknown
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Zircon
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Zircon
clear, blue, yellow
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Zirconium Silicate
ZrSiO4
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4.20-4.73
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1.92-1.98
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6-7.5
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Often heat treated.
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Opal
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Opal
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Hydrous Silicon Oxide
SiO2.nH2O
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1.25-2.23
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1.450
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5.5-6.5
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Sometimes oiled.
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Turquoise
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Turquoise
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Hydrated Copper Aluminum Phosphate
CuAl6(PO4)4(OH)8.5H2O
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2.40-2.9
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1.61-1.650
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5-6
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Often dyed.
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Moonstone
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Orthoclase Feldspar
white, peach
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Potassium Aluminum Silicate
KAlSi3O8
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2.55-2.61
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1.52-1.53
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5-6
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Malachite
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Malachite
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Hydrous Copper Carbonate
Cu2(CO3)(OH)2
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3.25-4.10
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1.65-1.91
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3.5-4
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Lapis Lazuli
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Lazurite
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Sodium Calcium Aluminum Silicate Sulfate(whew!)
(Na,Ca)8(Al,Si)12O24(S,SO4)
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2.5-3.0
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1.50-1.67
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5-5.5
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Sometimes dyed.
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Jade
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Jadeite
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Sodium Aluminum Iron Silicate
Na(Al,Fe+3)Si2O6
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2.95
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1.60-1.63
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6-6.5
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Nephrite jade is less costly than Jadeite.
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Carnelian, Bloodstone, Onyx, Agate, Jasper
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Chalcedony
Many colors and varieties
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Silicone Oxide
SiO2
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2.55-2.7
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1.53-1.82
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6.5-7
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Often dyed.
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